Several advantages are provided by drilling relatively high angle, deviated or lateral wells from a generally common wellbore such as a) access to the regular oil and gas reserves without additional wells being drilled from the surface, b) avoiding unwanted formation fluids, c) penetration of natural vertical fractures, and d) improved production from various types of formations or oil and gas reserves. Additionally, reentry of one or more lateral wells is often required to perform completion work, additional drilling, or remedial and stimulation work. Thus, lateral wells have become commonplace from the standpoint of new drilling operations and reworking existing wellbores.
Ordinarily, lateral well completion and/or reentry requires expensive downhole wireline surveys to accurately position the diverter or whipstock which is used to direct the boring or completion tool through a wall of a generally vertical wellbore into the adjacent formation. Without a survey, the lateral well formed may not be accurately recorded for purposes of reentry. For example, U.S. Pat. Nos. 4,304,299; 4,807,704; and 5,704,437 each describe a method and/or apparatus for producing lateral wells from a generally vertical common wellbore using conventional techniques and tools. In each instance, one or more lateral wells may be produced at a different depth and location in the common wellbore and reentered. Consequently, the whipstock must be repositioned at the new depth and location. Each time the whipstock is repositioned at a different depth and location, the change in depth and lateral orientation relative to a point of reference is recorded. In many applications using conventional threaded connections, the exact depth and location of each lateral well formed cannot be accurately or efficiently recreated using the same system and technique. As a result, a downhole directional survey is necessary to relocate the exact depth and location of each lateral well upon reentry.
Recognizing the disadvantages of the foregoing techniques, U.S. Pat. No. 2,839,270 and, more recently, U.S. Pat. No. 5,735,350 address the need for a more accurate method and/or apparatus for producing and reentering lateral wells without the need for a directional survey. For example, U.S. Pat. No. 2,839,270 describes a technique for selectively forming a lateral well through a wall of a common wellbore at a predetermined depth and lateral orientation by means of a supporting apparatus which includes apertures formed at predetermined locations in the supporting apparatus. The apertures determine the relative depth and lateral orientation of each lateral well and are prefabricated according to the particular common wellbore in which the supporting apparatus is installed. The whipstock is then positioned using one or more specially designed latches which engage a corresponding aperture designed for receipt of the respective latch.
Similarly, U.S. Pat. No. 5,735,350 describes a method and system for creating lateral wells at pre-selected positions in a common wellbore by means of a diverter assembly having a plurality of locator keys specially designed to engage a corresponding nipple formed in the wellbore casing having a unique profile. Although this technique may be employed in new and existing wells, it is expensive and, in some instances, inappropriate because the prefabricated keys and nipples are permanently and integrally formed according to the particular formation characteristics of the common wellbore in which the system is installed.
More recently, a system and method for use in a completed wellbore lined with casing was described in U.S. Pat. No. 6,427,777. This system uses a directional survey to position an anchor at a predetermined depth and lateral orientation relative to a longitudinal position and lateral position of the desired lateral well. Because a directional survey is used to position the anchor after the casing is set and secured, the exact location of a pre-formed opening in the casing is difficult to find. And, because the system is designed for completed wellbores, the system typically requires running equipment in the wellbore which is different than the equipment used to line and secure the wellbore with casing. Finally, the casing must be milled with a different type of bit than the bit used to drill through the formation when the system is used in a completed wellbore without pre-formed openings in the casing. As a result, the system must be run in the wellbore twice to form each lateral well.